Hudson is a town in Middlesex County, Massachusetts, United States. Before its incorporation as a town in 1866, Hudson was a suburb of the neighboring Marlborough, Massachusetts, and was known as Feltonville, and before that, Eastborough. From around 1850 until the last shoe factory burned down in 1968, Hudson was known as a "shoe town." At one point, the town had 17 shoe factories, many of them powered by the Assabet River, which runs through town.

According to the United States Census Bureau, the town has a total area of 11.8 square miles (30.7 kmē), of which 11.5 square miles (29.8 kmē) is land and 0.3 square mile (0.9 kmē) (2.87%) is water. The Assabet River flows through the town. On the border with Stow is Lake Boon, once a popular vacation spot but now a primarily residential neighborhood. On the border with Marlborough is Fort Meadow Reservoir, which at one time provided drinking water to both Hudson and Marlborough.

As of the census of 2000, there were 18,113 people, 6,990 households, and 4,844 families residing in the town. The population density was 1,574.4 people per square mile (608.1/kmē). There were 7,168 housing units at an average density of 623.0 per square mile (240.7/kmē).